This invention relates to a process for continuously producing a stiff board, which is made from a cement-like material reinforced by glass fiber, having a high density suitable for use as a building material such as for partitions between rooms, and to an apparatus used in the carrying out the process.
This invention also relates to a process for continuously producing a light strong stiff board, which is made from an air-dispersed cement-like material reinforced by glass fiber, suitable for use as a building material such as for fire-proof coverings, sound-proofing materials and partitions, and to an apparatus used in the working of the process.
This invention also relates to a process for continuously producing a laminated board suitable for use as a building material such as for a partition, which comprises overlaying the air-dispersed board on the above dense stiff board, and to an apparatus used in the working of the process.
Heretofore, in preparing a stiff cement board reinforced by glass fiber, there has been suggested a "premix method" by which a board is formed after mechanically mixing glass fiber, cement powder or slurry thereof; a method which comprises individually forming a cement slurry and glass fiber into layers and then laminating the two layers; and a "spray method" as used in preparing a reinforced plastic.
The reinforcement by glass fiber becomes most effective when glass fiber having a length of 25 - 50 mm is added to a matrix in an amount of 6 - 15%, and is homogeneously dispersed throughout the matrix and is preferably disposed two-dimensionally with respect to the flat face.
However, in using a "premix method," it is difficult to homogeneously disperse glass fiber through a matrix, and it is also difficult to incorporate glass fiber having a length longer than 10 mm in an amount of more than 3% by weight. Moreover, in such a method, the glass fiber is extensively damaged since it is mixed with the matrix under vigorous stirring, and the glass is disposed three-dimensionally whereby the reinforcement is less effective.
In using a method which comprises laminating a glass fiber layer with a cement layer, the adhering area between the glass fiber and the cement is small, and accordingly the total adhesive force between the two components is small whereby the reinforcement is less effective.
In using a "spray method" as used in preparing a reinforced plastic, it is difficult to disperse glass fiber homogeneously through a cement material and to obtain a smooth surface since the fluidity and other properties of the cement slurry are quite different from those of the polymer.
One of the conventional laminated boards having a cement material as a main component comprises cement-asbestos plates between which a light cement material is charged. Another one comprises laminating a cement-asbestos plate with a gypsum board. The former is prepared by charging a light cement material between cement-asbestos plates fixed at a predetermined distance. The latter is prepared by binding a cement-asbestos plate and a gypsum board by means of a binding agent. In both cases, the element materials are individually preformed, and thereafter are fixed into the final product. Thus, the conventional products are prepared by at least two steps, and therefore from the economical points of view the productivity is low.